The present invention relates to the technical field of mortars, concretes, and other compositions based on cement and/or plaster, i.e. generally hydraulic binders and compounds, and in particular to agents capable of modifying their rheological characteristics, in particular workability.
Workability can be defined as being the property of a mortar or cement slip or slag, or more generally of a hydraulic binder of remaining workable during as long a time as possible, i.e. of being capable of being displaced from one container to another, of being stored, of being pumped with ease or with relative ease, and of being transported to a site on which it is to be used, and of having analogous characteristics, and therefore of being usable for a prolonged period. That property can be evaluated by means of the fluidity time of the hydraulic binder. The essential influence of such agents lies in the fact that the viscosity of the slag or slip remains stable for a prolonged period. The viscosity is stable for a long period, but is not necessarily lower than with other substances.
Such agents should be distinguished from retarding agents whose function is to retard the setting of the hydraulic binder.
For a long time now, the person skilled in the art has being studying additives designed to be used as cement thinners without having any significant effect on the setting delay.
Thus, Patent EP 0 303 747 describes copolymers of (meth)acrylic acid (20% molar to 40% molar) and of hydroxyalkylated (meth)acrylic esters (80% molar to 60% molar) of high molecular weight (minimum of 70,000 g.mole).
Patent EP 0 556 061 describes copolymers of maleic anhydride and of surfactant monomers that are allylated, oxyalkylated, and functionalized by groups of short alkyls (1 to 4 carbons).
It is indicated that a mixture of such copolymers is capable of replacing advantageously the formulations described in Patent EP 0 490 681.
That patent describes an additive designed to improve the workability of cements and mortars and to improve workability time. That additive is constituted by a mixture of three components:
a lignosulfonate salt;
a copolymer of maleic anhydride and of an alkyl oxyalkylene allyl (for respective molar ratios varying in the range 1 to 3, and claimed molecular weights lying in the range 1,000 to 200,000); and
an anionic surfactant.
The person skilled in the art is acquainted with Patent WO 94/05606 which relates to a specific dispersing agent making it possible to reduce the quantity of bubbles in cements. That dispersion agent is a dispersant, water-soluble polymer which can be a polyacrylate grafted with a methoxy-polyethyleneglycol (methoxy-PEG), a copolymer of maleic anhydride functionalized with a methoxy-PEG, or a copolymer of maleic anhydride and of methoxy-PEG allyl.
That document also describes a viscosity-reducing agent function which can be an alkaline agent, an alkaline-earth agent, an amine of low molecular weight, or a urea or thiocyanate salt.
The person skilled in the art is also acquainted with Patent WO 95/09821 which describes a hydraulic cement additive designed to improve rheology, and defined as being derived from acrylic polymers. Such polymers are exclusively imidized acrylates obtained by thermal condensation of primary amines with polyacrylic acids (180xc2x0 C.xe2x80x942 hours of reaction) or by catalyzed reaction with dicyclohexylcarbodiimide (70xc2x0 C.xe2x80x944 hours of reaction). The substitution ratios claimed vary over the range 10% to 50%.
Similarly, Patent WO 95/16643 describes a thinning additive designed for hydraulic cements. That additive is chosen from terpolymers of alkyl-PEG (meth)acrylate, of (meth)acrylic acid, and of a sulfonated (meth)allyl monomer. Those polymers are obtained by radical polymerization and in aqueous medium.
Patent EP 0 725 043 is extremely general, claiming a large number of molecules obtained by implementing widely differing chemical methods, and no practical teaching can be discerned from that patent.
It would seem that document describes a dispersing agent for cement and mortar that limits shrinkage on drying, thus preventing cracks from appearing. The macromolecule is defined as being a polycarboxylic acid (and its salts) grafted or modified with oligoalkylene glycols and polyalkylene glycols.
The extremely general definition of the polyacids includes the following copolymers: styrene-maleic, allylether-maleic, diisobutylene-maleic, acrylic, and methacrylic.
The oligomers are ethers of low molecular weight that are widely used in paints as coalescence solvents.
The styrene-maleic anhydride and allyl-maleic copolymers are synthesized in the solvent and then the resulting polyanhydride is grafted by means of alcohols.
In the case of acrylics, oxyalkylated monomers are formed with acryloyl chloride, and they are then copolymerized in isopropanol in the presence of (meth)acrylic acid.
Patent EP 0 753 488 is also a patent that claims chemical structures very broadly. Those structures are described as being dispersing agents that are extremely effective in reducing workability problems, even for cements having very low water contents.
The polymers described are all obtained by direct radical polymerization. They are terpolymers of methacrylic or acrylic acid (6% to 60%), of a methacrylate or acrylate of alkoxy (C1 to C5) PEG (polyethylene glycol) (40% to 94%), and of a third monomer (0% to 10%).
The synthesis of each of the molecules is given in detail, and they are compared with molecules that are identical but of different polydispersity.
The person skilled in the art can also make reference to Patent EP 0 271 435 which concerns the synthesis of an additive for a hydraulic binder or compound. The product is defined as being a grafted polymer and is obtained by radically polymerizing an acrylic monomer in a medium constituted only by surfactants (polyethylene glycol: PEG, polypropylene glycol: PPG). The mixture is then diluted with water and then neutralized. No information is given about the grafting yields, but the effectiveness of the products was workability tested.
The products currently on the market correspond to the chemistry of the agents described in Patents EP 0 612 702, EP 0 792 850, EP 0 816 298, U.S. Pat. No. 5,362,829, U.S. Pat. No. 5,633,298 or in U.S. Pat. No.5,668,195. In the same chemistry of polyacrylic or grafted polyacrylate acids including oligoalkyleneglycol and/or polyalcohol chains and polyalkylene glycols, U.S. Pat. No. 5,660,626 describes dispersing agents for reducing the shrinkage of compositions of cements, mortars and concretes, which agents are active at low concentrations.
Unfortunately, all of those agents give workability characteristics that are not entirely satisfactory to the person skilled in the art.
Mention should also be made of French Patent Application No. 9808484 that is unpublished on the priority date of the present application, and that describes the use, with cements, of polycondensates obtained by causing polyethylene glycols and their derivatives to react with isocyanates and alcohols of low molecular weight so as to synthesize polymers that are soluble in water or partially soluble in water, which makes it possible to improve significantly the workability of mortars, concretes, and other compositions based on cement and/or on plaster, and defined as hydraulic binders or compounds. Such workability leads to an increase in the fluidity time of the resulting hydraulic compound, making it possible to use the compound for prolonged periods. The products described consist of polycondensates obtained by causing polyethylene glycols (PEGs) and their derivatives such as, for example, ethylene oxide and propylene oxide copolymers, to react with mono-, di-, or tri-isocyanates and optionally alcohols of low molecular weight.
The general state of the art shows that, outside the above-mentioned unpublished application, all of the new thinners designed to impart workability to cement are water-soluble acrylic or maleic and/or allyl polymers (unlike the prior art in which, as indicated above, lignosulfonates, sulfonated phenol-formol resins, and surfactants are used), and such polymers are weakly anionic and strongly functionalized by esters of alkoxy (short alkoxys having 1 to 4 carbons) polyethylene glycols groups. In the remainder of the description below, the letters PEG are used as an abbreviation for polyethylene glycol.
The closest prior art, outside the above-mentioned unpublished application would seem to be the Sandoz Patent EP 0 725 043, but that document describes only grafted polyacids, oligoalkyleneglycols and polyalkyleneglycols, in a ratio of 50/50 in % by weight.
In addition, a major drawback of the prior art, other than the above-mentioned unpublished application, lies in the presence of a carboxylic chain, because such a chain imparts a major retardant property. Unfortunately, although the industry wishes to increase the workability, i.e. the duration of use of a binder, it absolutely does not want setting to be retarded at the chosen moment of use.
The Applicant""s above-mentioned unpublished application has made significant progress by proposing a workability agent that does not retard or that hardly retards the setting time of the hydraulic binder.
However, there remains a major need in the industry in question for a workability agent for mortars, concretes, and other hydraulic binders, which workability agent offers further-increased workability properties. In the above review of the prior art, it appears that the properties involved are extremely sensitive and often antagonistic, which makes progress difficult.
In the invention, it has been discovered that radical co-polymerization of at least one ethylene monomer, having an alkoxy-polyalkylene glycol urethane function and more particularly alkoxy-PEG urethane, with at least one anionic monomer and at least one non-ionic monomer, optionally in the presence of alkoxy-PEG (meth)acrylate and of crosslinking agents, surprisingly imparts a significant improvement in workability, whereas the prior art makes no mention of the presence of monomers having alkoxy-polyalkylene glycol urethane functions, and more particularly of alkoxy-PEG urethane.
It has thus been discovered that the use, with mortars, concretes and other hydraulic binders, of acrylic copolymers containing at least one alkoxy-polyalkylene glycol urethane function, resulting in the synthesis of water-soluble polymers, makes it possible to increase significantly the workability of mortars, concretes, and other compositions based on cement and/or on plaster, such compositions based on cement and/or plaster being more generally defined as hydraulic compounds or binders. This workability results in an increase in the fluidity time of the resulting hydraulic compound, thereby making it possible for said compound to be used for a prolonged period.
The invention provides workability agents for mortars, concretes, and other hydraulic binders, said workability agents being characterized in that they consist of copolymers obtained by radical copolymerization of at least one alkoxy-polyalkylene glycol urethane ethylene monomer and more particularly alkoxy-PEG urethane with at least one anionic monomer and at least one non-ionic monomer optionally in the presence of alkoxy-PEG acrylate or methacrylate, said PEG (polyethylene glycol) being defined by a molecular weight greater than 300, and optionally in the presence of one or more ethylene monomers having at least two polymerizable double bonds, and also referred to as xe2x80x9ccrosslinking agentsxe2x80x9d.
The invention also provides hydraulic binders such as concretes, mortars, and mixtures based on cement and/or on plaster, each of them containing a workability agent of the invention.
The invention also provides the use of hydraulic binders containing the novel workability agent in construction, building, public works or in petroleum cements and petroleum service and supply industries.
The co-polymer constituting the novel workability agent of the invention for mortars, concretes and other hydraulic binders is prepared using known methods of performing radical copolymerization in solution, in emulsion, or in suspension on the mixture of the above-mentioned monomers, in the presence of a catalytic system and transfer agents that are known, implemented in appropriate quantities, the molecular weight of said copolymer being adjusted by known means such as, for example, temperature, catalyst content, presence or absence of transfer agents, or by any other means or combination of means known to the person skilled in the art.
The catalytic polymerization system, which can vary in quantity by weight in the range 0.1% to 10% relative to the total mass of the monomers, is desirably chosen from those which are water-soluble such as, for example, ammonium, potassium, or sodium persulfates, or peroxides or hydroperoxides such as, in particular, hydrogen peroxide, and optionally implemented with a known reducing compound such as, in particular sodium metabisulfite or metallic salts.
The chain transfer agent, whose quantity by weight may vary in the range 0% to 5% by weight relative to the total mass of the monomers used is desirably chosen from alkyl-mercaptans such as, for example, octanethiol, decanethiol, n-dodecanethiol, t-dodecanethiol, or from mercaptopropionic acid, mercaptosuccinic acid, thioglycolic acid, or mercaptoethanol or else secondary alcohols, certain alkyl halides or salts of acids of phosphorus of oxidation number less than 5, as well as various other additives known to the person skilled in the art, as chain limiters.
In the entire present application, the designations of the following abbreviations used are as follows:
PO4EGMA=ethylene glycol methacrylate phosphate
EGMA=ethylene glycol methacrylate
PEG 350=polyethylene glycol of molecular weight 350
PEG 750=polyethylene glycol of molecular weight 750
and by analogy, any number after the letters PEG indicates the molecular weight of said PEG
EA=ethyl acrylate
Acryl=acrylamide
MAA=methacrylic acid
AA=acrylic acid
TEA=triethanolamine
TDI=toluene diisocyanate
IPDI=isophorone diisocyanate
In the present invention, the following monomers are polymerized:
a) at least one anionic monomer;
b) at least one non-ionic monomer;
c) at least one alkoxy-polyalkylene glycol urethane ethylene monomer, sometimes referred to as a xe2x80x9cspecial urethane monomerxe2x80x9d;
d) optionally an alkoxy-PEG (meth)acrylate; and
e) optionally one or more ethylene monomers having at least two polymerizable double bonds and referred to as xe2x80x9ccrosslinking agentsxe2x80x9d;
the sum of the quantities of the monomers a), b), c), d) and e) being equal to 100%.
The anionic monomer(s) is/are chosen from acrylic acid, methacrylic acid, acrylamido-methyl-propane-sulfonic acid, alkylene glycol acrylate or methacrylate sulfonate or sulfate or phosphonate, or phosphate, itaconic acid, maleic anhydride, sodium methallylsulfonate, sulfonic styrene acid, and more particularly chosen from acrylic acid, methacrylic acid, acrylamido-methyl-propane-sulfonic acid, ethylene glycol methacrylate phosphate, or ethylene glycol acrylate phosphate.
The non-ionic monomer(s) is/are chosen from acrylamide or methacrylamide or their derivatives, C1 to C5 alkyl-esters of acrylic or methacrylic acids, oxyalkylated alkoxy acrylates or methacrylates (the number of alkylene oxides lying in the range 1 to 5), vinyl acetate, vinylpyrrolidone, styrene, or alphamethyl-styrene, and more particularly chosen from ethyl acrylate or acrylamide.
The alkoxy-polyalkylene glycol urethane monomer(s) is/are chosen from the reaction products of methoxy-polyalkylene. glycol reacting with a polymerizable unsaturated isocyanate, and more particularly from the reaction products of methoxy-PEG reacting with an acrylic isocyanate or a methacrylic isocyanate or a vinyl or allyl isocyanate.
The novel agents of the invention are thus products that can be termed partially PUR (polyurethane). The compounds in unpublished French Patent Application No. 9808484 are said to be xe2x80x9c100% PUR (polyurethane)xe2x80x9d, are non-ionic, and are obtained by polycondensation, whereas those of the present invention are obtained by radical polymerization and are partially anionic.
In the present invention, at least 3% of special urethane monomer is used.
In the invention, the monomers are used in the following proportions in the copolymer:
for the monomer a), in the range 1% to 50% by weight, and preferably in the range 5% to 40% by weight;
for the monomer b), in the range 2% to 65% by weight, and preferably in the range 5% to 60% by weight;
for the monomer c), in the range 3% to 65% by weight, and preferably in the range 10% to 50% by weight;
for the monomer d), in range 0% to 90% by weight, and preferably in the range 0% to 70% by weight; and
for the monomer e), in the range 0% to 5% by weight, and preferably in the range 0% to 3% by weight;
the sum of the quantities of the monomers a), b), C), d) and e) being equal to 100%.
The present invention thus uses the replacement of an ester function serving to key onto the alkoxy-PEG group with a urethane bridge which improves significantly the workability properties, within the above limits of the urethane functions in the copolymers of the invention.
The copolymers of the invention may or may not be crosslinked.
If they are crosslinked, it is possible to use up to about 5% by weight, relative to the total mass of the monomers, of crosslinking agents well known to the person skilled in the art such as methylene-bis-acrylamide or MBA, methylene-bis-methacrylamide, allyl acrylate, tetrallyloxyethane, triallylcyanurates or TACs, allyl ethers obtained from polyols such as in particular sorbitol, sucrose or the like such as triallylated pentaerythritol, pentaerythritol triacrylates, ethylene glycol dimethacrylate or EDMA, trimethylolpropane triacrylate, and di- or tri-vinylbenzenes, and analogous compounds.
The copolymers of the invention may be used in salt form or in partially neutralized form, in particular obtained by sodium ions, but equally possibly by ions of potassium, magnesium, calcium, lithium, ammonium, or triethanolamine and other amines. The invention thus also provides these agents and their uses.
For fabricating alkoxy-polyalkylene glycol urethane monomers that are reaction products of alkoxy-polyalkylene glycol reacting with a polymerizable unsaturated isocyanate, one of the following is preferably but non-limitingly used as the polymerizable unsaturated isocyanate: dimethyl isopropenyl benzyl isocyanate, methacryloyl isocyanate, or allyl-isocyanate, or the reaction product of a diisocyanate such as, for example, toluene diisocyanate (TDI) or isophorone diisocyanate (IPDI) reacting with a polymerizable unsaturated alcohol preferably chosen from ethylene glycol acrylate, ethylene glycol methacrylate, or allyl alcohol.
For fabricating the alkoxy-polyalkylene glycol urethane monomers, the following is preferably but non-limitingly used: an alkoxy-polyethylene glycol, the alkyl chain being chosen from chains having 1 to 5 carbon atoms, although the methyl group is preferable, the length of the oxyethylated chain being chosen in the range of molecular weights from 350 to 5,000, and more preferably in the range of molecular weights from 500 to 1,500.
The copolymers of the invention are of molecular weight corresponding to a specific viscosity of less than substantially 2, and preferably lying in the range 0.3 to 1.6, values of above substantially 2 corresponding to poor workability.
The specific viscosity of the copolymer is symbolized by the letter xcex7 and it is determined as follows:
A copolymer solution is taken so as to obtain a solution corresponding to 2.5 g of dry polymer neutralized with soda and to 50 ml of a bipermuted water solution.
Then, a capillary viscometer of Baume constant equal to 0.000105 placed in a bath whose temperature is thermostatically set at 25xc2x0 C. is used to measure the flow time of a given volume of the above-mentioned solution containing the copolymer, and the flow time of the same volume of the bipermuted water solution without said copolymer. It is then possible to define the specific viscosity xcex7 by means of the following relationship:   η  =                                                        (                              flow                ⁢                                  xe2x80x83                                ⁢                time                ⁢                                  xe2x80x83                                ⁢                of                ⁢                                  xe2x80x83                                ⁢                the                                                                                                        copolymer                ⁢                                  xe2x80x83                                ⁢                solution                            )                                          -                                                  (                              flow                ⁢                                  xe2x80x83                                ⁢                time                ⁢                                  xe2x80x83                                ⁢                of                ⁢                                  xe2x80x83                                ⁢                the                                                                                                        bipermuted                ⁢                                  xe2x80x83                                ⁢                water                ⁢                                  xe2x80x83                                ⁢                solution                            )                                                  flow      ⁢              xe2x80x83            ⁢      time      ⁢              xe2x80x83            ⁢      of      ⁢              xe2x80x83            ⁢      the      ⁢              xe2x80x83            ⁢      bipermuted      ⁢              xe2x80x83            ⁢      water      ⁢              xe2x80x83            ⁢      solution      
The capillary tube is generally chosen such that the flow time of the bipermuted water solution not containing the copolymer is approximately in the range 90 seconds to 100 seconds, thus giving specific viscosity measurements of very high accuracy.
Other characteristics and advantages of the invention will appear more clearly on reading the following description with reference to the accompanying drawing, in which FIG. 1/1 diagrammatically shows a xe2x80x9cworkability meterxe2x80x9d or xe2x80x9cvibratorxe2x80x9d.
The following examples illustrate the invention without, however, limiting its scope.